Water heater

ABSTRACT

Water heaters having a combustion chamber with a water jacket and having flue tubes extended from the combustion chamber with surrounding water tubes, the water tubes being connected with the water jacket and the circulation being arranged to provide for passage of the water through the water tubes surrounding the flue tubes and through the water jacket in counterflow relation to the flow of products of combustion through the combustion chamber and through the flue tubes.

United States Patent Black 51 June 13, 1972 [54] WATER HEATER [72]Inventor: Robert B. Black, 2925 Denver Street, Corpus Christi, Tex.78404 [22] Filed: Aug. 6, 1970 [21] Appl. N0.: 61,775

[52] US. Cl. ..122/l36 R, 122/156 [511 int. Cl. ..F22b 7/00 [58] Fieldof Search ..122/24,.115, 130, 136, 156,

[56] References Cited UNITED STATES PATENTS I 2,838,102 6/1958Reimers.., ..122/24 X 1,993,748 3/1935 Noack ..122/24 2,040,090 5/19361161mm ..122/24 2,513,551 10/1951 Denker et a1. .....122/34s x 2,607,3258/1952 Denker et a1. .....122/34s x 3,143,160 8/1964 Rydberg ..122/24 xPrimary Examiner--Kenneth W. Sprague Attorney-Synnestvedt & LechnerABSTRACT 12 Claims, 12 Drawing Figures PAWBM a 3 m2 SHEET 2 BF 4INVENTOR. #05:}?7 52 51,404

WATER HEATER This invention relates to water heaters and is concernedwith very high efficiency water heater equipment in which the efficiencyof use of thefuel approaches to within a couple of per cent of thetheoretical maximum.

Water heaters of the prior art are in general of two known types.Perhaps the most common type of water heater now in use is one in whicha water tank is provided with a combustion chamber 'at the vbottom andhas a flue extended upwardly through the tank for indirect heat transferto the water and for discharge of products of combustion at the top. Inthis form of heater, commonly referred to as a storage heater, theproducts of combustion are. commonly discharged at quite hightemperatures, so that the overall efficiency is not more than about 80percent. In another well known type of water heater, a water coil ispositioned'in acombustion chamber or passage for hot products ofcombustion, and while this form of I heater is effectivefor rapidlyincreasing the water temperature, it also discharges products ofcombustion at relatively high temperatures and has an efficiency whichat the maximum reaches about 80 percent.

It is a major objective of the present invention to provide a waterheater having an exceptionally high efficiency rate. In accordance withthe invention, the gases or products of combustion released from theheater are not more than a few degrees higher, even as low as 1 F., thanthe temperature of the incoming cold water. This represents a thermalperformance which no conventional water heaters now known are capable ofapproaching. Indeed it is not unusual for conventional water heaters torelease their products of combustion well above the boiling point ofwater, in many cases running even as high as 500700 F.

The foregoing striking improvement is achieved according to the presentinvention by utilizing certain novel combinations of elements or devicesand by observing certain operating conditions, all of which will befully explained hereinafter.

One of the important structural features used according to the presentinvention is a tube-within-a-tube heat transfer element in which theproducts of combustion are delivered through the interior of the inneror flue tube and in which the water to be heatedis fed through the outeror water tube in the annular space surrounding the inner tube in adirection in counterflow to thedirection of flow of the products ofcombustion in the inner tube. This structural feature is used incombination with a combustion chamber having a water 'jacket, the waterjacket being connected in series with the water'tube.

Provision is also made for effecting combustion of the fuel in thecombustion chamber at a high temperature so that the combustion of thefuel is virtually complete before entry of the products of combustioninto the flue tube. This is accomplished in part by utilizing a linerwithin the combustion chamber providing a dead air space between thewater jacket and the interior region of the combustion chamber where thefuel is burned. Still further, conditions of pressure in the combustionchamber and flue tube, feed rates and proportions of the equipment areestablished so that the temperature of the products of combustion beingdischarged are very close to the temperature of the inlet or feed waterinto the heater. All of these factors cooperate in achieving the highdegree of efficiency obtainable in accordance with the presentinvention.

Still another object of the invention is to provide a tube bundleincorporating a plurality of flue tubes each with a surrounding watertube, which bundle is arranged as a unitary structure and provided withseparable connection means by which the bundle may readily be removedfrom and reassembled with the system, either for the purpose of cleaningthe tubes or for the purpose of replacing the used bundle with a newone.

How the foregoing and other objects and advantages are attained willappear more fully from the following description referringto theaccompanying drawings illustrating several preferred embodiments of theinvention and, in which:

FIG. 1 is a somewhat diagrammatic outline view of a water heater systemaccording to one embodiment of the present invention;

FIG. 2 is a sectional view through the combustion chamber, water jacket,and tube-within-a-tube heat transfer element arranged according to theembodiment of FIG. 1;

FIG. 3 is a partial transverse sectional view taken as indicated by thesection line 33 on-FIG. 2;

FIG. 4 is an enlarged sectional view of a detail taken as indicated bythe section line 4-4 on FIG. 3;

FIG. 5 is a sectional view through a combustion chamber and multipletube-within-a-tube heat transfer system, arranged according to a secondembodiment and illustrating certain parts in elevation;

FIG. 6 is a transverse sectional view taken as indicated by the sectionline 6-6 on FIG. 5;

FIG. 7 is a sectional view through the combustion chamber and a tubebundle of a third embodiment of the invention;

FIG. 8 is a transverse sectional view taken as indicated by the sectionline 88 on FIG. 7;

FIG. 9 is a partial transverse sectional view taken as indicated by theline 9-9 on FIG. 7;

FIG. 10 is a view similar to 'FIG. 7' but illustrating still anotherembodiment of the invention;

FIG. 11 is a sectional view taken as indicated by the line l1ll on FIG.10; and I FIG. 12 is an elevational view illustrating the arrangement ofair inlet passages and control damper employed in the embodiment of FIG.10. 4

Although any embodiment of the equipment may be positioned with themajor components such as the combustion chamber and heat transfer tubesextended either horizontally or vertically, the arrangement shown inFIGS. 1 to 4 is advantageously arranged horizontally, whereas thearrangements shown in FIGS. 5 to 12 are most desirably arrangedvertically, for reasons which will further appear.

Considering first the somewhat diagrammatic outline view of FIG. 1, theequipment includes several components which are designated in thatfigure in a general manner. Thus, the

equipment includes a combustion chamber indicated at 7 hav-- ing atube-within-a-tube heattransfer device 8 extended from the combustionchamber. A compressor unit diagrammatically indicated at'9 serves todeliver fuel and air under pressure through the inlet connection 10 intothe combustion chamber 7, the air being supplied to the compressorthrough the connection 11 and the fuel through the connection 12. Theflue tube of the heat transfer device 8 is extended as indicated at 13for discharging the products of combustion to atmosphere. Water entersthe system through the connection 14 and flows through the device 8 andalso through the jacket for the combustion chamber as described morefully hereinafter, the hot water being discharged through the pipe 15.

As seen in FIGS. 2, 3 and 4, the combustion chamber has a wall 16, inthis case a cylindrical wall which is surrounded by another cylindricalwall 17 spaced therefrom so as to provide a water jacket between the twowalls. The fuel and air inlet or supply line 10 enters the left hand endof the combustion chamber behind the distributor plate 18 which extendstransversely across the combustion chamber and which is provided withports 19 (see particularly FIGS. 3 and 4) through which the fuel and airpasses into the main part of the combustion chamber. The ports 19 areinclined in the manner indicated in order to cause the entering fuel andair to partake of a swirling motion as they enter the region wherecombustion occurs. Combustion may be initiated by an electric spark plugsuch as indicated at 20 which ordinarily need only be employed at thecommencement of operation, the continuance of the combustion beingnormally maintained under the influence of the generated heat as thefuel and air are forced into the combustion zone.

At the end of the combustion chamber opposite'to the inlet 10, a fluetube 21 is extended for ultimate discharge through the connection 13already referred to. This flue tube is surrounded by a water tube 22,the water tube being spaced from the flue tube to provide an annularwater flow passage between the two tubes. This annular passage isconnected with the water jacket space as is plainly shown in FIG. 2. Thewater inlet 14 is connected with the annular water flow passage at theend thereof remote from the combustion chamber so that the water beingheated flows through the annular passage toward the combustion chamberand then through the water jacket surrounding the combustion chamber tothe passage 23 from which the discharge line 15 is extended. Coppertubing is desirably employed forthe tubes 21 and 22.

FOr maximum conservation of heat, it is preferred to provide aninsulative coating or lagging such as indicated at 24 covering thecombustion chamber and heat transfer tube units.

From the foregoing it will be observed that the water passes incounterflow heat transfer relation to the combustion gases and productsof combustion within the flue tube 21 and the combustion chamber 16,this counterflow relationship being maintained all the way from the coldor feed water inlet 14 to the hot water outlet 15.

For the purpose of assisting maintenance of high combustion temperaturewithin the interior of the combustion chamber and consequentsubstantially complete combustion of the fuel within that chamber, aliner 25 is provided within the combustion chamber, this liner, in theembodiment shown in FIGS. 1 to 4 being of cylindrical form but ofsmaller diameter than the combustion chamber 16 itself so as to providea dead air space between the liner and the inside surface of thecombustion chamber wall 16. The liner is advantageously made of somespecial alloy steel having high heat resistance, such as the so-calledNo.32l stainless steel which is not only highly temperature resistant,but which also possesses high resistance to oxidation. This arrangementof liner 25, dead air space, combustion chamber wall 16 and thesurrounding water jacket allow sufficient radiation from the combustionchamber to prevent the refractory liner from disintegrating while at thesame time providing for relatively high liner temperature, for instanceof the order of l,300-I ,800 F.

In the system illustrated in FIGS. 1 to 4, it is contemplated that acombustion chamber pressure be established which is substantiallyelevated as compared with atmospheric pressure, for instance a pressurerunning anywhere from about 4 PSI up to about 80 PSI. As an example ofother factors usable in a system of the kind shown in FIGS. 1 to 4, itmay be noted that inner and outer tubes having outside diameters of theorder of three-eighths and three-fourths inch respectively are suitablewhere a single tube-within-a-tube unit 21-22 is employed. In such aninstallation it would also be contemplated to employ a tube unit ofconsiderable length, for instance of the order of 25 feet. Such a unitmay either be straight or coiled. In an installation of theseproportions, considerable pressure is desirable in order to effect feedof the products of combustion through the flue tube, and this isadvantageously achieved by the use of a compressor such as indicated at9 in FIG. 1 to which both the fuel and air are admitted, so that thefuel and air mixture are introduced into the combustion chamber under apressure such as referred to above. The fuel employed may be gas or mayalternatively be atomized fuel oil or the like.

During operation of a system of this kind, the pressure results inrelatively high velocity flow through the flue tube and this contributestwo important results. First, the high velocity maintains such acondition of turbulence at the surface of the flue tube that there is noopportunity for a stagnant boundary layer to form, thereby aiding inmaintaining the high efficiency of heat transfer through the wall of theflue tube. Second, the high velocity and turbulence of the flow throughthe flue tube prevents the accumulation of scale or other depositswithin the flue tube, thereby maintaining the high efficiency of heattransfer for long periods of time without the necessity for any cleaningor replacement ofthe flue tube.

With flue and water tubes of diameters such as those referred to above,the velocity of flow of water may also be relatively high, therebyhelping to reduce deposits of scale or the like on the water side of thesystem.

With equipment of the kind just described, a very high rate of waterheating is practical, even with a combustion chamber and tube unithaving a total weight of the order of 20 pounds. For instance in oneinstallation of this kind, it was found that 120 gallons of water perhour were delivered at 1 25 F with a water input temperature of F., andthat the products of combustion were discharged at 76 F., only 1 F.higher than the input water.

Similar results are also obtainable with the modified system now to bedescribed with reference to FIGS. 5 and 6.

Here a combustion chamber 26 is positioned at the bottom of theequipment, this chamber having an inner liner 27 of the kind describedabove and having an outer wall 28 providing a water jacket, as before.

Tangential inlet pipes 29-29 (see FIG. 6) are provided for introductionof air and fuel into the combustion chamber. These pipes 29 are open toatmosphere to receive the ambient air, and fuel may be injected orotherwise delivered through the nozzles 30-30 which are supplied bymeans of the supply pipe 31. It will be noted that the inlet pipes 29are arranged at the bottom of the combustion chamber and provide for introduction of fuel and air with a swirling motion.

One of the principal differences between the arrangement of FIGS. 1 to 4and the arrangement of FIGS. 5 and 6 lies in the use in the latterembodiment of a plurality of tube-withina-tube units, two such unitsbeing here shown and each comprising an inner flue tube 32 and an outerwater tube 33. The flue tubes are extended upwardly for communicationwith the common chamber 34 with which the inlet 35 of the exhaust blower36 is connected. The discharge from this blower is indicated at 37. Inthe system of FIGS. 5 and 6, therefore, instead of compressing the fueland air in advance of entry into the combustion chamber, the air isadmitted to the combustion chamber at ambient pressure, accompanied byinjection of fuel, so that combustion will occur in this instancesubstantially at atmospheric pressure. Because of this pressurecondition, an ordinary pilot light may be utilized for initiating thecombustion, it being unnecessary to resort to an ignition system, suchas a spark plug, capable of operating under pressurized combustionconditions.

In the system of FIGS. 5 and 6, the inlet or feed water enters throughthe supply line 38 into a header 39 with which the annular flow passageswithin the water tubes 33 communicate, the discharge ends of those flowpassages again being con nected with the water jacket surrounding thecombustion chamber as in the first embodiment. The hot water isdischarged from the bottom end of the water jacket through theconnection 40. As in the first embodiment the combustion chamber andtube units are here also provided with a lagging 41 which insulatesthose parts and reduces heat losses.

It will be understood that an arrangement such as shown in FIGS. 5 and 6may utilize any desired number of tube-withina-tube units. The provisionof more than one such unit has distinctive advantages, including thefact that the overall length of the tube units need not be as great.Indeed for a production capacity of the general order of magnitude abovereferred to, whereas a single tube about 25 feet long was required, witha multiple tube arrangement four tubes of about 4-6 feet in length wouldsuffice. The employment of a plurality of the tube units also hasanother important advantage, namely the fact that combustion need nottake place at substantially elevated pressures, and in view of this, itis not necessary to employ a compressor in the air and fuel supply line.Instead, it becomes a practical to employ an exhaust blower such asindicated at 36 connected to receive the products of combustion beingdischarged, or even to eliminate the blower entirely, as is contemplatedin one of the embodiments hereinafter described.

Itis to be kept in mind that the high-efficiency of heat transfer andthe relatively low exhaust gas temperature are factors which makepossible the use of a simple exhaust blower such as shown in FIG. 5connected in the exhaust side of the system, the employment of a blowerat the exhaust side of a water heater system not being practical whererelatively high exhaust gas temperatures are encountered.

Although the velocity of the products of combustion is not as high inthemultiple tube arrangement of FIGS. 5 and 6, as in the single tubearrangement of FIGS. 1 to 4, nevertheless the system of FIGS. 5 and 6has many of the advantages of the arrangement of FIGS. 1 to 4. Witheither system the arrangement of the present invention provides muchgreater water heatingcapacity in proportion to bulk and weight than ispossible with conventional water heaters, such as those referred toabove.

Turning now to the embodiment of FIGS. 7, 8 and 9, it is first pointedout that the arrangement here shown, like the arrangement of FIGS. 5 and6, is a multiple tube arrangement,

certain features of which-are of special importance in providing ease ofmaintenance and replacement of the tube bundle.

As shown in FIG. 7, the combustion chamber is defined by the wall 42,this being surrounded by the spaced wall 43 providing a water jacket. Aliner 44 is provided within the chamber, in the general manner describedabove with reference to the liners 25 and 27 of FIGS. 2 and 5. Anignition plug 20 is here also used in the manner of the firstembodiment. An apertured plate 45 is positioned in the entrance end ofthe combustion chamber, being arranged in the general manner of theplate 18 of the first embodiment, the apertures serving to distributethe fuel and air entering the combustion chamber from the fuel and airsupply connection 46.

A plurality of flue tubes 47 are here employed, these tubes beingprovided with upper and lower tube plates 48 and 49. Each flue tube 47is surrounded by a water tube 50 which are alsoprovided at their upperand lower ends with'tube plates 5 l and 52. l

The tube plates 48 and 51 at the upper end of the tube bundle are spacedfrom each other and the tube plate 51 is provided with a generallycylindrical wall portion 53 cooperating with the plates to define aninlet water header with which the water supply line 54 is connected.

Similarly at the lower end of the tube bundle, the tube plate 52 isprovided with a cylindrical portion 55 which cooperates with the plates49 and 52 to provide an outlet water header the edges of whichcommunicate with the water jacket lying between the inner and outercombustion chamber walls 42 and 43. I

At the upper and lower ends of the tube bundle, the header structuresare provided with bolting flanges 56 and 57. The flange 56 is adapted tobe separably connected with the flange 58 formed peripherally of the gasmanifold 59 which receives the'gases discharging from the upper ends ofthe flue tubes 47. The flange 57 is adapted to be separably connectedwith the flange 60 formed on the outer combustion chamber wall 43. Thisprovides for separation of the tube bundle with respect to thecombustion chamber. 7

The tube bundle arrangement as described just above provides forconvenient handling of the entire tube bundle asa unit, which is ofimportance for purposes of maintenance and also for replacementpurposes. Indeed, the tube bundle may be of such simple form andconstruction that it may even be considered almost in the category of adisposable unit. Therefore in a water heater installation of the kindhere described, instead of discarding an entire water heater when eitherflue or water tubes become clogged or surface coated with deposits orimpurities, the tube bundle may merely be replaced, the remainder of theequipment being retained and continued in use.

As seen in FIGS. 7 and 9, the flange 60 includes not only the annularportion thereof projecting radially outwardly from the combustionchamber Wall 43, but also the annular portionindicated at 60a whichprojects inwardly of the inner combustion chamber wall 42, these twoportions of this flange being interconnected by means of spoke-likeparts 61 which are circumferentially spaced from each other so as toprovide free flow of water from the lower header of the tube bundle intothe upper edge of the water jacket surrounding the combustion chamber.The tube plate 49 and the mounting flange 57 at the lower end of thetube bundle may similarly be interconnected by spoke-like partscircumferentially spaced from each other so as not to interfere withwater flow from the header into the jacket. This form of constructionthus assures proper interpositioning of the lower ends of the flue tubeswithin the water tubes while at the same time providing adequate crosssectional water flow area from the lower header into the jacket. Thewater offtake from the heater is indicated at 62 toward the bottom ofFIG. 7.

At the top of FIG. 7 an offtake blower 36 having a discharge connection37 is shown as being connected with the gas manifold 59 in the samegeneral manner as described above with reference to FIG. 5. 7

Turning now to the embodiment illustrated in FIGS. l0, l1 and 12, it isfirst to be noted that the tube bundle, comprising parts 47-53 and 55-57may be identical with those described above with reference to FIGS. 7 to9. The embodiment of FIGS. 10 to 12 thus also contemplates the use of aunitary tube bundle providing ease of maintenance and replacement.Certain other parts of the arrangement of FIGS. 10 to 12 are alsosimilar to FIGS. 7 to 9, including the provision of a water supplyconnection 54 associated with the upper water header, the gas manifold59 with its bolting flange 58 adapted for cooperation with the flange56.

In the embodiment of FIGS. 10 to 12, however, it will be noted that noblower 36 is associated with the upper end of the system, the dischargeconnection 63 being arranged to discharge to atmosphere.

The arrangement of FIG. 1t) also utilizes a combustion chamber formed byinside and outside walls 42 and 43, with an inner liner 44 and having abolting flange 60 projecting radially outwardly, as well as a flange 60aprojecting radially inwardly. An ignition plug 20 is also provided inFIG. 10.

The fuel and air inlet arrangements of FIGS. 10 to 12, however, aredifferent from those provided in any-of the other arrangementsdescribed. Thus, as seen in FIG. 10, two spaced plates 64 and 65 areprovided at the lower end of the combustion chamber, the two platesbeingpositioned in spaced relation. The upper plate 64 is provided withventuri apertures 66, and the lower plate with fuel jet nozzles 67, anozzle 67 being aligned with each venturi passage 66. The fuel nozzlesare supplied with fuel under pressure, for instance gas, through thefuel supply line 68.

An annular series of air inlet openings 69 are provided through thewalls 42 and 43 of the combustion chamber in registry with the spacelying between the venturi plate 64 and the nozzle plate 65, so that thefuel jet nozzles and the venturi passages serve to induce inflow of airrequired for combustion. An annular damper 70 (see FIGS. 10 and 12)having a series of openings 71 surrounds the combustion chamber in theregion of the airinlet opening 69 and provides for control of the crosssectional flow area for admission of air. An operating handle such asindicated at 72 may be provided for regulating the damper.

The water jacket lying between the inner and outer combustion chamberwalls 42 and 43 is continued down to the bottom of the equipment, atwhich point the hot water discharge connection 62 is arranged, in thegeneral manner already described with reference to some of the otherfigures.

The plan pattern of fuel jet nozzles and also of the venturi passages isclearly shown in FIG. I 1. Advantageously this plan pattern may besimilar to the plan pattern of the flue and water tube units, the latterof which is shown in FIG. 8 in relation to the embodiment of FIGS. 7 to9.

With respect to the embodiments of both FIGS. 7 to 9 and FIGS. 10 to 12,it will be understood that if desired heat insulation or lagging mayalso be applied surrounding the tube bundle and the combustion chamber,for instance in the general manner indicated at 24 in FIG. I and at 41in FIG. 5.

With respect to all of the embodiments illustrated and described, itwill be understood that many specific details of structure have not beenshown in the drawings, these being unnecessary to an understanding ofthe nature of the invention. For example, many portions of the wallssurrounding the combustion chamber may desirably be formed of amultiplicity of parts assembled and welded together in any desiredmanner. For the sake of simplicity and clarity in illustration anddescription, only those portions of the structure having a significantbearing upon the features of novelty have been illustrated anddescribed.

In considering the operation of all of the embodiments disclosed in thisapplication, it is to be noted that while any of the water heatersillustrated and described may be used to deliver heated water to astorage tank, it is preferred to completely dispense with the storage ofheated water, because hot water storage necessarily involves loss ofheat and this in turn reduces the overall efficiency of the system. Itis therefore contemplated according to the present invention that thewater heater be operated only in accordance with the demand for hotwater, rather than in accordance with the water temperature, as in theprior art storage heater systems. In most situations this necessarilyinvolves intermittent operation, and with this in mind it iscontemplated that the equipment of the invention be employed with anautomatic control system for initiating and terminating the feed of fueland air in response to the demand for hot water. For example in adomestic or home installation, it is contemplated to utilize a controlsystem responsive to the flow of water from the heater, for instanceresulting from the opening of a hot water valve or spigot. Such a flowresponsive control device is indicated diagrammatically at 62a in FIG.10.

Automatic controls of the kind-just referred to are known and are notdisclosed herein as the details thereof form no part of the presentinvention per se. Such controls have been known heretofore in connectionwith the type of prior art water heater hereinabove referred to in whicha water coil is positioned within a combustion chamber or combustionproducts passage. However, in contrast to such prior known waterheaters, all embodiments of the heater of the present inventioncontemplate the use of flue tubes surrounded by water tubes which, in asense, represents an inversion of the heat transfer system, as comparedwith the prior water coil type of heater referred to. By employing fluetubes of relatively small cross sectional flow area surrounded by watertubes defining a water flow passage of relatively small cross sectionalarea, much greater thermal efficiencies are obtainable, than is possibleby placing a water coil in a gas or other combustion chamber, as hasbeen done heretofore.

All embodiments of the heater according to the present invention arealso clearly distinguishable from the other well known type of waterheater above described (commonly referred to as a storage heater) for anumber of reasons, including the following. First, the prior storagetype of heater has a combustion chamber at the bottom and a flueextended upwardly through the water storage tank. Because of thenecessity for relying upon this water tank for storage purposes, it isnecessarily of very large volume in relation to the hot water dischargepipe and also in relation to the flue channel for the hot gases leavingthe combustion chamber. These relationships do not admit of highly effcient heat transfer conditions, in consequence of which a very high BTUloss occurs because of the discharge of the gases at a relatively hightemperature in relation to the input temperature of the water.Preferably the cross sectional water flow area of the water tubes is notsubstantially greater than the cross sectional flow area of the hotwater delivery line extended from the heater. In a case where the crosssectional water flow area approximates the cross sectional flow area ofthe hot water delivery line, the rate of flow through the heater willsubstantially correspond to the rate of flow of water through thedelivery line. While it is not necessary to maintain the water flow areathrough the heater approximately the same as the water flow area throughthe connnected delivery pipe, nevertheless it is preferred to keep thewater flow area through the heater within a limit of several times thewater flowarea of the pipe, for instance within two or three times thewater flow area of the pipe.

Thus, the system of the present invention is clearly distinguishablefrom the prior art so-called storage" systems in that the presentinvention deliberately avoids the storage function with a view toeliminating the heat losses which are incident both to the storagefunction itself and also to the low efficiency imposed upon the systemas a result of the attempt to effect heat transfer from the hot gases tothe large bulk or volume of water necessarily contained in a storagetank.

The arrangements of the invention are thus capable of achieving almostperfect combustion efficiencies and extremely high thennal efficiencies,going far beyond the capabilities of the conventional types of waterheaters. These efficiencies are due to several factors, some of whichhave already been mentioned'and further including the use of thecounterflow principle in the tube-within-a-tube units, the use ofcounterflow not only within those tube units but also within the 1jacket surrounding the combustion chamber, the water flow path beingextended serially through the tube units and then through the waterjacket. Still another factor of importance in achieving the efficienciesreferred to is the high temperature established in the combustionchamber and the consequent virtually complete combustion, before theproducts of combustion enter the flue tubes. The establishment ofoperating conditions providing for discharging of combustion products ata temperature within a couple of degrees of the temperature of input ofthe water is also ofimportance in achieving the efficiencies referredto.

As above noted, although the velocities of water and products ofcombustion in the systems of FIGS. 5 to 12 are not as high as in thesystem of FIGS. 1 to 4, nevertheless even in the system of FIGS. 10 to12, one or the other or both of those velocities are relatively high ascompared with conventional water heaters of the kinds referred to above.Therefore, even in the arrangement of FIGS. 10 to 12, there is aminimization of soot and mineral deposits in the gas and water sides ofthe system, as compared with prior water heaters.

Although in all of the embodiments described and illustrated, the fueland air both enter through the same inlet or inlets into the combustionchamber, it will be understood that the fuel and air may be introducedthrough separate inlets either in a system in which combustion isestablished under pressure, or in a system in which combustion occurs atsubstantially ambient pressure.

From the foregoing it will be seen that various important features ofthe present invention may be utilized in systems of a wide variety oftypes, especially with respect to the introduc tion of the fuel and air.Thus, a relatively high pressure type of system may be employed, as inFIGS. 1 to 4, or a relatively low pressure blower type of system, as inFIGS. 5 and 6 or 7 to 9, FIGS. 5 and 6 illustrating the application ofthe blower to the input side of the system, and FIGS. 7 to 9illustrating the application of the blower to the output side. In FIGS.10 to 12 various features of the invention are shown as applied to asystem in which no blower or compressor is used for the air, theintroduction of the fuel and air and the flow of the gases through thesystem being effected only by virtue of the fuel feed or supply line,such as the normal pressure available in gas supply tanks or mains.

From the foregoing it will also be seen that water heaters according tothe present invention are well adapted to a variety of uses, includingboth domestic and commercial. For example, the heaters of the presentinvention are well adapted for use in supplying the hot water used inhomes.

Water heaters according to the present invention are also especiallywell adapted to use in a situation where a large volume of water is tobe heated on a once-through" basis, i.e., without storage, for instancethe heating of water for a swimming pool. in such an installation theheater may be used for long periods -of time without accumulation ofmineral deposits, because high water temperatures are not needed.

I claim:

1. A water heater comprising a combustion chamber, inlet means forintroducing fuel and air into one end of the combustion chamber, a fluetube for discharging products of combustion from the other end of thecombustion chamber, a water jacket surrounding the combustion chamberand having an inlet in a region remote from the fuel and air inlet andhaving an outlet in a region adjacent to the fuel and air inlet, a linerin the combustion chamber spaced from the chamber wall to provide a deadair space between the water jacket and the interior of the combustionchamber where the fuel and air is burned, and a water tube surroundingthe flue tube and providing an annular water flow passage surroundingthe flue tube, the water tube. having a water inlet at its end remotefrom the combustion chamber and being connected with the water inlet tothe water jacket surrounding the combustion chamber and thereby providefor counterflow of combustion products through the combustion chamberand flue tube in relation to the flow of water through the annularpassage surrounding the flue tube and through the water jacketsurrounding the combustion chamber.

2. A water heater as defined in claim 1 and further including acompressor for introducing the fuel and air under compression throughthe fuel and air inlet into the combustion chamber.

3. A water heater as defined in claim 1 and further including a blowerin the discharge from the flue tube providing for drawing of the fueland air through the inlet into the combustion chamber.

4. A water heater as defined in claim 1 in which the fuel and air inletmeans comprises a fuel jet, a venturi passage through which the fuel jetdelivers fuel into the combustion chamber,

- and an inlet for combustion air communicating with the inlet end ofthe venturipassage.

5. A water heater comprising a combustion chamber, inlet means forintroducing fuel and air into one end of the combustion chamber, a fluetube for discharging products of combustion from the other end of thecombustion chamber, a water jacket surrounding the combustion chamberand having an inlet in a region remote from the fuel and air inlet andhaving an outlet in a' region adjacent to the fuel and air inlet, awater tube surrounding the flue tube and providing an annular water flowpassage surrounding the flue tube, the water tube having a water inletat its end remote from the combustion chamber and being connected withthe water inlet to the water jacket surrounding the combustion chamberand thereby provide for counterflow of combustion products through thecombustion chamber and flue tube in relation to the flow of waterthrough the annular passage surrounding the flue tube and through thewater jacket, and pump means for establishing combustion under pressureand forced circulation of combustion products from the combustionchamber through the flue tube.

6. A water heater comprising a combustion chamber, inlet means forintroducing fuel and air into the combustion chamber, a plurality offlue tubes for discharging products of combustion from 'the combustionchamber, a common chamber into which the flue tubes discharge, a blowerhaving its inlet connected with said common chamber providing fordrawing of the combustion products through the flue tubes, a water tubesurrounding each flue tube and providing an annular water flowpassagesurrounding the flue tube, and aninlet header for feeding water into thewater tubes at the ends thereof remote from the combustion chamber andthereby provide for counterflow of the water through the annular flowpassage in relation to the flow of combustion products through the fluetubes. I

7. A water heater comprising a combustion chamber, inlet means forintroducing fuel and air into the bottom of the combustion chamber, aflue tube extended upwardly from the combustion chamber for dischargingproducts of combustion from the top of the combustion chamber, a waterjacket surrounding the combustion chamber and having an inlet in theregion of the top of the combustion chamber and having an outlet in theregion of the bottom of the combustion chamber, and a water tubesurrounding the flue tube and providing an annular water flow passagesurrounding the flue tube, the water tube having a water inlet at itsupper end and being connected with the water inlet to the water jacketsurrounding the combustion chamber and thereby provide for upwardcounterflow of combustion products through the combustion chamber andflue tube in relation to the downward flow of water through the annularpassage surrounding the flue tube and through the water jacket. I

8. A water heater as defined in claim 7 and further including a blowerconnected with theupper end of the flue tube providing for drawing ofthe fuel and air through the inlet into the bottom of the combustionchamber.

9. A water heater as defined in claim 7 in which a plurality of fluetubes and surrounding water tubes are provided and further including acommon flue tubedischarge chamber, and

an exhaust blower connected with said common chamber and providing forflow of combustion products through the flue tubes.

10. A water heater comprising a combustion chamber, inlet means forintroducing fuel and air into the combustion chamber, a tube bundleincluding a plurality of flue tubes for discharging products of.combustion from the combustion chamber and further including a pluralityof water tubes surrounding the flue tubes and each providing an annularwater flow passage surrounding a flue tube, the tube bundle having fluesheets and tube sheets at each end spaced from each other to provideinlet and outlet water headers, and separable connection means betweenthe tube bundle and the combustion chamber providing for removal andreplacement of the tube bundle with respect to the combustion chamber.

11. A water heater comprising a combustion chamber, a water jacketsurrounding the combustion chamber, inlet means for introducing fuel andairinto the combustion chamber, a plurality of flue tubes fordischarging products of combustion from the combustion chamber, a commonchamber into which the flue tubes discharge, a water tube surroundingeach flue tube and providing anannular water flow passage surroundingthe flue tube, and inlet and outlet headers for feeding water throughthe water tubes, the water inlet header having water supply means andthe water outlet header having connection means for delivering waterfrom the outlet header into the water jacket surrounding the combustionchamber, said connection means being separable to provide for removaland replacement of the water tubes.

12. A water heater comprising a combustion chamber, inlet means forintroducing fuel and air into the combustion chamber, a flue tube fordischarging products of combustion from the combustion chamber, a waterjacket surrounding the combustion chamber, and a water tube surroundingthe flue tube and providing an annular water flow passage surroundingthe flue tube, the water tube having a water inlet at its end remotefrom the combustion chamber and being connected with the water jacketsurrounding the combustion chamber and thereby provide for flow of waterserially through the annular passage surrounding the flue tube andthrough the water jacket, the fuel and air inlet means comprising a pairof spaced plates one having fuel jet nozzles extended therethrough andthe other having venturi passages extended therethrough in alignmentwith the fuel jet nozzles, the space between said plates comprising anair chamber for supplying air to the venturi passages.

1. A water heater comprising a combustion chamber, inlet means forintroducing fuel and air into one end of the combustion chamber, a fluetube for discharging products of combustion from the other end of thecombustion chamber, a water jacket surrounding the combustion chamberand having an inlet in a region remote from the fuel and air inlet andhaving an outlet in a region adjacent to the fuel and air inlet, a linerin the combustion chamber spaced from the chamber wall to provide a deadair space between the water jacket and the interior of the combustionchamber where the fuel and air is burned, and a water tube surroundingthe flue tube and providing an annular water flow passage surroundingthe flue tube, the water tube having a water inlet at its end remotefrom the combustion chamber and being connected with the water inlet tothe water jacket surrounding the combustion chamber and thereby providefor counterflow of combustion products through the combustion chamberand flue tube in relation to the flow of water through the annularpassage surrounding the flue tube and through the water jacketsurrounding the combustion chamber.
 2. A water heater as defined inclaim 1 and further including a compressor for introducing the fuel andair under compression through the fuel and air inlet into the combustionchamber.
 3. A water heater as defined in claim 1 and further including ablower in the discharge from the flue tube providing for drawing of thefuel and air through the inlet into the combustion chamber.
 4. A waterheater as defined in claim 1 in which the fuel and air inlet meanscomprises a fuel jet, a venturi passage through which the fuel jetdelivers fuel into the combustion chamber, and an inlet for combustionair communicating with the inlet end of the venturi passage.
 5. A waterheater comprising a combustion chamber, inlet means for introducing fueland air into one end of the combustion chamber, a flue tube fordischarging products of combustion from the other end of the combustionchamber, a water jacket surrounding the combustion chamber and having aninlet in a region remote from the fuel and air inlet and having anoutlet in a region adjacent to the fuel and air inlet, a water tubesurrounding the flue tube and providing an annular water flow passagesurrounding the flue tube, the water tube having a water inlet at itsend remote from the combustion chamber and being connected with thewater inlet to the water jacket surrounding the combustion chamber andthereby provide for counterflow of combustion products through thecombustion chamber and flue tube in relation to the flow of waterthrough the annular passage surrounding the flue tube and through thewater jacket, and pump means for establishing combustion under pressureand forced circulation of combustion products from the combustionchamber through the flue tube.
 6. A water heater comprising a combustionchamber, inlet means for introducing fuel and air into the combustionchamber, a plurality of flue tubes for discharging products ofcombustion from the combustion chamber, a common chamber into which theflue tubes discharge, a blower having its inlet connected with saidcommon chamber providing for drawing of the combustion products throughthe flue tubes, a water tube surrounding each flue tube and providing anannular water flow passage surrounding the flue tube, and an inletheader for feeding water into the water tubes at the ends thereof remotefrom the combustion chamber and thereby provide for counterflow of thewater through the annular flow passage in relation to the flow ofcombustion products through the flue tubes.
 7. A water heater comprisinga combustion chamber, inlet means for introducing fuel and air into thebottom of the combustion chamber, a flue tube extended upwardly from thecombustion chamber for discharging products of combustion from the topof the combustion chamber, a water jacket surrounding the combustionchamber and having an inlet in the region of the top of the combustionchamber and having an outlet in the region of the bottom of thecombustion chamber, and a water tube surrounding the flue tube andproviding an annular water flow passage surrounding the flue tube, thewater tube having a water inlet at its upper end and being connectedwith the water inlet to the water jacket surrounding the combustionchamber and thereby provide for upward counterflow of combustionproducts through the combustion chamber and flue tube in relation to thedownward flow of water through the annular passage surrounding the fluetube and through the water jacket.
 8. A water heater as defined in claim7 and further including a blower connected with the upper end of theflue tube providing for drawing of the fuel and air through the inletinto the bottom of the combustion chamber.
 9. A water heater as definedin claim 7 in which a plurality of flue tubes and surrounding watertubes are provided and further including a common flue tube dischargechamber, and an exhaust blower connected with said common chamber andproviding for flow of combustion products through the flue tubes.
 10. Awater heater comprising a combustion chamber, inlet means forintroducing fuel and air into the combustion chamber, a tube bundleincluding a plurality of flue tubes for discharging products ofcombustion from the combustion chamber and further including a pluralityof water tubes surrounding the flue tubes and each providing an annularwater flow passage surrounding a flue tube, the tube bundle having fluesheets and tube sheets at each end spaced from each other to provideinlet and outlet water headers, and separable connection means betweenthe tube bundle and the combustion chamber providing for removal andreplacement of the tube bundle with respect to the combustion chamber.11. A water heater comprising a combustion chamber, a water jacketsurrounding the combustion chamber, inlet means for introducing fuel andair into the combustion chamber, a plurality of flue tubes fordischarging products of combustion from the combustion chamber, a commonchamber into which the flue tubes discharge, a water tube surroundingeach flue tube and providing an annular water flow passage surroundingthe flue tube, and inlet and outlet headers for feeding water throughthe water tubes, the water inlet header having water supply means andthe water outlet header having connection means for delivering waterfrom the outlet header into the water jacket surrounding the combustionchamber, said connection means being separable to provide for removaland replacement of the water tubes.
 12. A water heater comprising acombustion chamber, inlet means for introducing fuel and air into thecombustion chamber, a flue tube for discharging products of combustionfrom the combustion chamber, a water jacket surrounding the combustionchamber, and a water tube surrounding the flue tube and providing anannular water flow passage surrounding the flue tube, the water tubehaving a water inlet at its end remote from the combustion chamber andbeing connected with the water jacket surrounding the combustion chamberand thereby provide for flow of water serially through the annularpassage surrounding the flue tube and through the water jacket, the fueland air inlet means comprising a pair of spaced plates one having fueljet nozzles extended therethrough and the other having venturi passagesextended therethrough in alignment with the fuel jet nozzles, the spacebetween said plates comprising an air chamber for supplying air to theventuri passages.